Spaceflight Now notes that the 12 hours and 39 minutes between the launches of SBIRS GEO 6 on an Atlas V and KPLO on a Falcon 9 from Cape Canaveral was the shortest interval between two launches from the base since 1967-09-07, when a Thor-Delta and Atlas-Centaur were launched 9 hours and 53 minutes apart.
The all time record turnaround between launches from Cape Canaveral is 1 hour and 40 minutes, which was done four times in 1966 when Agena target vehicles were launched on Atlas boosters and then Gemini spacecraft were launched on Titan II rockets to rendezvous and dock with them.